With the end of affirmative action, MIT's incoming class better reflects merit

“M.I.T. officials took pains to make the point that the enrollment decline in historically underrepresented minority students did not mean that the university had admitted underqualified students in the past.”

“Officials said that the change in the composition of the class also had nothing to do with the reinstatement, two years ago, of the SAT as an entrance requirement.”

If these two hypotheses are untrue according to MIT officials, just what are they thinking caused the drop?